Whole number

Whole numbers are the set of positive integers; no fraction, decimal, or negative numeral can be a whole number. Whole numbers include 0 and all the cardinal numbers. In mathematical notation, we can specify the set of whole numbers as:

{0, 1, 2, 3, 4, 5, 6, ...}

Whole numbers can also be expressed using a number line:

Note that only the points on the number line that have labeled values are whole numbers. Depending on the definitions used, whole numbers may be synonymous with natural numbers.

Natural numbers vs whole numbers

Two main definitions of natural numbers are used. One of the definitions is the set of numbers:

{0, 1, 2, 3, 4, 5, 6, ...}

In this case, the definition of natural numbers is identical to that of whole numbers.

The other commonly used definition of natural numbers is the set of numbers:

{1, 2, 3, 4, 5, 6, ...}

The only difference between this set and the one above is that it doesn't include zero. In this definition of natural numbers, whole numbers are used to indicate that 0 is included in the set of numbers.

Whole number vs integer

Integers include negative values. Aside from this difference, the set of whole numbers and integers include the same values. This means that a whole number is always an integer, but an integer is not always a whole number.

The set of whole numbers:  {0, 1, 2, 3, 4, 5, 6, ...}
The set of integers:  {..., -3, -2, -1, 0, 1, 2, 3, ...}

If we took the absolute value of any integer, we would get a whole number.

Is 0 a whole number?

Yes 0 is a whole number. This is simply by definition. It is included in the set of whole numbers as part of the definition.